1. Field of The Invention
The invention relates to a novel process for the preparation of 6-hydroxy-2,5,7,8-tetraalkyl-2-(4-aminophenoxymethyl)chromans (aminochroman) of the general formula: ##STR5## wherein R denotes a lower alkyl group having 1 to 4 carbon atoms.
2. Background Art
It is known from European Published Patent Application No. 207,581 to prepare aminochromans of the general formula I by first converting a tetraalkyl-2-(4-nitrophenoxymethyl)chroman-4-one into the corresponding chroman-4-ol using sodium borohydride, in a further step dehydrating the chroman-4-ol to the chroman-3-ene in the presence of p-toluenesulphonic acid and in the last step hydrogenating both the nitro group and the chromene double bond using a hydrogenation catalyst to give the final product. This reaction has the disadvantage that a considerable need for working up arises between the individual reaction steps, which impedes conversion of the synthesis to industrial scale. Additionally, reduction using sodium borohydride is expensive in comparison with catalytic reductions and is problematic from an ecological point of view as the resulting effluents are polluted with boron.